1,720,970 research outputs found
Sinergia tra mappe di qualità delle acque e correnti superficiali nella determinazione strutture di circolazione
No full textLa mappatura delle variabili di qualità delle acque, quali la clorofilla-a (CHL-a) e la Temperatura Superficiale del mare (SST-Sea Surface Temperature) viene effettuata routinariamente dai sensori satellitari per l’osservazione della terra. I satelliti forniscono una
visione sinottica di questi parametri, praticamente in tempo reale e su larga scala. Ad ogni modo, le relazioni tra i parametri di qualità delle acque e le forzanti fisiche che ne determinano le variabilità spazio-temporali, quali campi di vento e di correnti, necessitano uno studio approfondito
A hidden Markov approach to the analysis of space-time environmental data with linear and circular components
No full textThe analysis of bivariate space-time series with linear and circular components is
complicated by (1) multiple correlations, across time, space and between variables, (2)
different supports on which the variables are observed, the real line and the circle, and
(3) the periodic nature of circular data. We describe a multivariate hidden Markov
model that includes these features of the data within a single framework. The model
integrates a circular von Mises Markov field and a Gaussian Markov field, with
parameters that evolve in time according to a latent (hidden) Markov chain. It allows to
describe the data by means of a finite number of time-varying latent regimes,
associated with easily interpretable components of large-scale and small-scale spatial
variation. It can be estimated by a computationally feasible Expectation-Maximization
algorithm. In a case study of sea currents in the Northen Adriatic sea, it provides a
parsimonious representation of the sea surface in terms of alternating environmental
states
Tidal currents in the Malta - Sicily Channel from high-frequency radar observations
No full textTwo years of sea surface current measurements acquired since August 2012 by High-Frequency SeaSonde radars over the relatively shallow shelf area dividing the Maltese Islands from Sicily (the Malta - Sicily Channel), are used to characterize the surface tidal currents in the region. Tidal currents are generally weak and concentrated in the semidiurnal and diurnal bands, barely exceeding 3cms-1 in the semidiurnal band (M2, S2), and below 6cms-1 in the diurnal band (K1, O1). In the middle part of the basin, the M2 currents oscillate along the main Channel axis; on the contrary the S2 oscillations are oriented along the energetic Atlantic Ionian Stream (AIS) flow. Diurnal tides have a more circular pattern, also following the AIS path and with a significant intensification in proximity of the shelf break, thus suggesting a substantial contribution from internal tides in the region. Phase contours suggest the presence of amphidromic points for both the semidiurnal and diurnal constituents, located in the central area of the Channel for S2, O1 and K1, but slightly shifted towards north-west for the M2 component
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Lagrangian Coherent Structures in the Trieste gulf.
No full textOne serious issue in Environmental Science and Engineering concerns the prediction of the fate of contaminants released in a water body. A possible way to tackle this problem consists in forecasting pollutant trajectories from velocity-field data sets obtained by measurements or numerical simulations. A shortcoming of such a traditional approach is the high sensitivity to initial conditions. Another way to understand transport in complex fluid flows comes from a new mathematical tool: Lagrangian Coherent Structures (LCS). The idea of using Lagrangian Structures rose as a meeting point between non-linear dynamics and fluid mechanics. It provides the means to identify material lines that shape trajectory patterns, dividing the flow field into regions with different dynamical behaviours.
The objective of this study is the detection of Lagrangian Coherent Structures in the Gulf of Trieste. LCS are calculated from the 2D surface velocity field measured by the coastal radars of the TOSCA (Tracking Oil Spills & Coastal Awareness network) project. Blobs of simulated particles are subjected to chaotic stirring (transport and stretching) that is in agreement with the detected LCS.
In the TOSCA project drifters were deployed, too. Therefore, a simple simulation of some of these drifters was carried out. The trajectory of the simulated drifters diverge from the real one: this result is due to the chaotic transport of passive tracers. However, the separation becomes more evident when velocity fields are less accurate because of lack of measurements, previously filled with nearest neighbourhood interpolation. In the light of such results, the use of LCS could be helpful in understanding the trajectory followed by drifters and passive tracers in general, because they can point out the directions along which transport is likely to develop
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Barriere Lagrangiane superficiali nel Golfo di Trieste
No full textUn problema di grande importanza nell’Ingegneria Ambientale consiste nella previsione del trasporto e della concentrazione di contaminanti rilasciati all’interno di un corpo idrico, per garantire la conservazione della sua naturalità da un punto di vista ecologico (preservazione della risorsa) e naturalistico (conservazione di flora e fauna). Tali problemi di mescolamento si differenziano in funzione delle caratteristiche del moto del fluido stesso (moto laminare o turbolento, presenza di convezione e dispersione) e vengono generalmente affrontati tramite lo schema diffusivo alla Fick. Chiaramente la conoscenza delle velocità del campo di moto gioca un ruolo fondamentale nell’impostazione di tali problemi. E’ però vero che la conoscenza del campo di velocità in ogni punto e in qualsiasi istante temporale risolve effettivamente qualsiasi problema legato al moto di un fluido? In verità, le informazioni di maggiore interesse, ovvero legate al trasporto di materia nel campo di moto, derivano dalla conoscenza del campo di velocità, ma non sono contenute già direttamente in esso
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